text:
How can I tell how far I am from a cloud?
So the other day as I was flying, I started to wonder:

All pilots should be familiar with basic VFR cloud clearance requirements in 14 CFR 91.155 (and if not, then go study now!).  When flying piston airplanes, we probably spend most of our time in the Class E below 10,000 ft. arena:

This is great and all, but how can we actually determine how far away we are (especially vertically)?
I thought about using a sextant and some "simple math":

Unfortunately, I need to know my actual distance TO the cloud as well as my angle...  A quick Google search found one of these, but I'm not so sure how it will work with a cloud:

In all seriousness though, how can we stay legal and safe when operating VFR in the vicinity of clouds?

Always wanted to get my hands on one of these and try them out: http://en.wikipedia.org/wiki/File:Bosch_PLR25.jpg

TLAR - That Looks About Right

The answer, as best I can discern it from my training & my own experience, is "You can't!" -- every instructor I've flown with has said that cloud clearances are the most inadvertently-busted regulation, even when pilots are doing their best to obey the requirements.
Our eyes and brain are really good at judging distance relative to landmarks and objects of known size (that's how we can tell we're on a "3 mile final" or "8 miles out"), but without known references our ability to estimate distance quickly falls apart, and there simply aren't that many useful landmarks in the sky.

Judging lateral distance to clouds is, at least in my experience, generally easier than vertical distance - as long as you're a fair distance away from the cloud anyway.
You can roughly estimate the ground position of a cloud pretty easily (and if you can't you can always use its shadow and be pretty close). You can also usually find features on the ground of known size (runways, for example: You can get the length of the longest runway at a field from your handy VFR sectional), and figure out how many of those are between you and the cloud's ground position.
Also if you're doing this whole pilotage-and-navigation thing right you know where you are on the chart, and you can visually estimate the ground position of a cloud pretty easily (again if all else fails use its shadow and you'll be close). Break out your plotter and you can figure out how many miles away you are from the cloud (but inside about 3 miles this is going to get pretty difficult, and with your head in the cockpit mucking about with the chart and plotter you may wind up inside the cloud by the time you're done working up your estimate!).
A final close-in technique for clouds at your altitude is to use your wing. You know your aircraft's wingspan, and you can also say that roughly half that value is the length of one wing. Figure out how many "wings away" the cloud is, and do the math -- of course if you're at a distance where you can do that kind of visual estimation you're likely to be close to the cloud clearance limits.

Judging vertical distance is harder.  The usual advice if you're below the clouds is to get the cloud heights from a local airports ATIS or AWOS and use that as a guide.  If you're above the clouds PIREPs for cloud tops serve the same purpose.
Visually if you're above the cloud the same skills you use to judge your height above a runway will work. The catch is those skills really only work when you're within about 1000 to 2000 feet (i.e. "By the time you can really judge the distance you may already be too close!").
Coming up from below a cloud you're basically relying on judging your closing speed to an object of unknown / nebulous size: As you approach the cloud it's going to get bigger, but you don't really know how big it's going to get before you wind up inside it.
As a final visual cue in any direction, remember that clouds aren't clearly-defined boundaries - Often you'll see little wispy streaks of cloud around you as you're getting closer to the cloud you're trying to avoid (particularly when approaching from below). This is a pretty definitive indication that you're probably closer to the cloud than you should be, and you should start heading away from the cloud before you wind up inside it.

I think the best bottom-line practical advice I've ever gotten on cloud clearances, loosely paraphrased from a couple of the local CFIs: "Just stay way the heck away from clouds until you're instrument rated and on an IFR flight plan." and "If you think you might be too close to a cloud, get further away!" -- the latter probably being what the FAA is getting at with their statutory distance requirements.

While distances are hard for many people to estimate, time is much easier for many people to estimate.  Pull out your trusty E6B, and work out the distance in terms of seconds.
For example, at a cruising speed of 110Kts (typical for many small GA student planes),

3 Miles is 1 minute 30 seconds
2000 feet is 10 seconds.

So if you cannot see where you'll be in 1:30, visibility is too low.
If you can fly to a cloud in less than 10 seconds, you're too close.

Edit
Flying Magazine essentially said the same thing in "Judging VFR Cloud Distances"

Unfortunately, it is also really hard to estimate where I will be in relation to the cloud in 10 seconds as well.  Or how can I tell whether or not a cloud is 500 feet above me?

You really don't know where you'll be in 10 seconds?  (How do you make it to the bathroom in time?) A cloud should not be able to jump out of nowhere and gobble you up in less than 10 seconds!  You should know your plane's climb rate... likely around 800-1000 FPM.  If you can climb into a cloud in less than 30 seconds, you're too close.

Yes, but will I be there in 10 seconds or 30 seconds or 5 seconds?  Sometimes (especially in a widespread overcast area) it is nearly impossible to tell how far away you are because you have no visual reference to determine your relative position.

Also, I agree that "if I can climb into a cloud in less than 30 seconds" that I am too close.  However, without actually doing it, I am still trying to visually estimate the distance.  This means nothing.

One of the biggest challenges is that clouds are often very hazy. Gauging depth is really hard.

Lastly, this regulation is there to keep you safe.  Just because the FAA can't see you doesn't mean that it's safe to skim the clouds.  When an IFR flight pops out of the cloud head on right in front of you, it is a problem regardless.

Sometimes you can look at the shadows on the ground to see how far apart they are.

It's a difficult skill to acquire.  Think of the cloud clearance requirements as a guideline.  Do your level best to comply with them but know that there is really no simple way to judge your true distance from a cloud.It's a see-and-avoid world for the VFR pilot.  The cloud clearance requirements are virtually impossible to enforce and the visibility mins are only slightly less difficult!  All the feds are asking for is for VFR pilot to remain reasonably far away from clouds given the regime in which the plane is operating.  Planes moving quickly require more distance from clouds in order to see-and-avoid other planes.In Class B and in G/day below 10k, just stay of of clouds.  You can't be deviating a mile out of the way for a cloud in Class B...you'd really screw up ATC's plan.  All the little and slow planes fly in Class G during the day and under 10,000'...so just stay clear of clouds.Above 10,000'?  Stay a mile away.  There are some fast planes up there and they need room to react to a possible collision.Everywhere else?  Three miles is sufficient.  Mooneys, Bonanzas, Lancair 320/360...they're pretty fast but really only need about half a mile to avoid a collision.


text:
How can I see the revision history of a particular FAR?
For instance, I don't remember paragraph 61.51(e)(iii) at all from way back when I studied it to determine when I could log PIC time.  I'm fairly certain that it has been added since then (actually, there was no sport pilot license back then so I know that it has at least been changed), but I would like to know when it was changed and what the changes were.
At the bottom of the reg, it includes this:

[Doc. No. 25910, 62 FR 16298, Apr. 4, 1997; Amdt. 61-103, 62 FR 40897,
July 30, 1997; Amdt. 61-104, 63 FR 20286, Apr. 23, 1998; Amdt. 61-110,
69 FR 44865, July 27, 2004; Amdt. 61-124, 74 FR 42549, Aug. 21, 2009;
Amdt. 61-128, 76 FR 54105, Aug. 31, 2011]

This tells me when it was amended, but not what was amended.
Does the FAA make that information available?

Changes to federal aviation regulations are listed on the FAA’s Regulatory & Guidance Library (RGL) at http://rgl.faa.gov/:

From the home page, click on the database titled "Code of Federal Regulations"
On the left, in the navigation tree, select one of the branches under "Historical CFR" (for example, "By Part")
On the right, expand the items leading to the regulation that you are looking for (in this case Part 61)
Scroll down to the regulation that you are looking for (61.51) and it will list the original version and all of the revisions:

Each revision is a link which takes you to the regulation as of that version, with links to the NPRM's and dockets so that you can see what has been changed!

I was digging for an answer to another question, and came across an answer to my own question here!

You can find this information with a bit of digging.
Hit up the GPO (Government Printing Office) here.
Choose the date range you want to look up.
Then choose the Title of the CFR you want (Aviation stuff is Title 14 CFR), and drill down until you find the Part you want, and it will give you some meta data about the change, and then the actual text of the change.
There might be an easier way, but, it is the federal government, so maybe not. :)
To answer your specific question, here is the link. (Click on the "Text" link for full details)

The only drawback here is you need to know the date range you're interested in - there's no way (I can find) to say "Show me all the changes to 14CFR91", and nothing like the "black line" indicating changes in the paper FAR/AIM from ASA. This is the one-and-only thing I miss about the paper version.

@voretaq7 Well, you can get the specific date of the change from the quote that I posted above (which is at the bottom of every regulation on ecfr.gov).

@Canuk I'll look at this a little more closely, but the link that you posted was for a change to 61.58, and not 61.51.

@lnafziger Yes, I suppose you could look up each change listed in the amendment list. But dangit we're pilots - we're supposed to be lazy and spoiled and have automation to do this sort of thing for me while someone slips us coffee through a pass-thru in the armored door! :-)

@Inafziger, I had written up this big thing and then realized I didn't specifically answer your question! So I looked up the last change mentioned on 61.51, but I guess I got the wrong one still! So, I guess you have to really want it! :)

So how do you find the docket?  It contains all of the changes and more, right?

Another good answer has already been given to this question, but this answer will address specifically how to see the documents you've referenced in the list of sources attached to your answer.

[Doc. No. 25910, 62 FR 16298, Apr. 4, 1997; Amdt. 61-103, 62 FR 40897,
  July 30, 1997; Amdt. 61-104, 63 FR 20286, Apr. 23, 1998; Amdt. 61-110,
  69 FR 44865, July 27, 2004; Amdt. 61-124, 74 FR 42549, Aug. 21, 2009;
  Amdt. 61-128, 76 FR 54105, Aug. 31, 2011]

"FR" means "Federal Register", and the "Federal Register" is available on-line, at last back through the mid-80's if not much further back.  The information in the list includes the page number (16298 in the first item in the list) and the volume number, which you don't really need (62 in the first item in the list).
Let's say I want to check the first source in the list above.  Google "Federal Register April 4 1997".  Select one of the hits that starts with a url "loc" (Library of Congress) or "gov.info.gov".  Use the link to download the April 4 1997 edition of the Federal Register.  (Example: https://www.govinfo.gov/content/pkg/FR-1997-04-04/pdf/FR-1997-04-04.pdf ) Go to page 16298.  There it is!  It is a Final Rule that actually spans pages 16219-16367.  You can read all about not only WHAT the FAA changed, but WHY they changed it-- how they justified it in terms of economic costs, safety benefits, etc; what other alternatives were considered, what kind of response they received to their original Notice Of Proposed Rule Making, what was the date of the original Notice of Proposed Rule Making and in which issue of the Federal Register was it published, etc.
Update-- if you read the FARs with this on-line source, the Federal Register references are actually attached to working links-- https://www.law.cornell.edu/cfr/text/14/chapter-I
Also, if you wish to see the FARs as they existed at any given date, here's how to do it--
Go to the government's webpage of cfr's on-line--
https://gov.ecfr.io/cgi-bin/ECFR?page=browse
In the box on the lower right, browse down to "Title 14" and hit "go"
Browse down to the part you are interested in-- e.g. part 91
There it is--
To see older versions, click on the "Browse/ Search Previous" button in the upper left.
However, it appears you'll only be able to navigate back as far as Jan 1, 2015.
Also, it does not seem to be easy to stay focused on one particular FAR (eg 91.157) as you move around to various dates.
It is also possible to find an on-line ebook of the entire FAR for some years, which you may be able to read for free.  Do a "google" search using the "books" option, searching for something like "FAR" or "FAR/AIM", "ebook", and the year of interest.
As far as seeing the revision history of one particular FAR goes, method suggested in the answer starting "Changes to federal aviation regulations are listed on the FAA’s Regulatory & Guidance Library (RGL)" is a good one, but it too is limited in how far back in time you are able to follow the revision history of any given FAR.  Certainly, for many regulations, it will not allow you to look back as far as the September 1993 "alphabet reorganization" of the national airspace system. To see further back in time, going directly to the Federal Register is often the best way to go, if you know the date and page number to go to.
The Federal Register may also be searched for NPRM's dealing with a given topic, etc.  This is a good way find information about regulatory changes that were proposed, then dropped.  "Google" isn't very effective as a search engine for the Federal Register.  A temporary subscription to a search engine offered by a company called Hein Online is a better way to go.  Some libraries, especially university libraries, may have a subscription that patrons may use.

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text:
Where can I find detailed dimensions of an aircraft engine compressor blade?
I am currently working on the modeling of blade/casing interactions in aircraft engines. The work is carried out in partnership with a company, therefore, there is a limited amount of it that could be published openly.
Are there any OpenSource compressor or turbine blade designs available (e.g. NACA airfoil profiles for wings)? Where could I find detailed dimensions and material properties?
The idea would be to use it for publication purposes, thus displaying relevant characteristics and realistic behaviors, while keeping all the confidential data of the company internally.

Since nobody's answered this yet, I'll take a stab at it.
I tried to find some dimensions for you online, but struggled.
Here's a thought though, could you just buy one?
For example - £35:

This is a Rolls Royce Olympus 593 Turbojet engine High Pressure Compressor Vane. This is a flown item that powered BAs Concorde fleet and the blade shows signs of use.
It was manufactured by Rolls Royce and has the Olympus 593 part number B430542.
The dimensions of this item in centimetres are approximately 15.5 x 4 x 4 and it weighs approximately 400g.

There are lots more on eBay too.
You asked about material — one listing says the Tornado's Rolls Royce RB199 engine is made from titanium.

seems like a reasonable solution if used blades are available at such (relatively) reasonable prices. You would have to go over them with a micrometer to get the dimensions (which could be a little time-consuming if the airfoil shape is complex), but it seems do-able.

@DannyBeckett Actually, this is a pretty good idea. Even if for super small compressor blades the measurement procedure would be particularly hard, specially for complex airfoil shapes (as suggested by @voretaq7).
I was wondering, if these blades are on the market, do they fall under the public domain ? Can the data then be used freely for publication purposes ?

@Nicolas That would be a question for your attorney - you shouldn't ask for (or trust) legal advice from an aviation site :-)

@voretaq7 Fair enough ! :-)

3D scanning is becoming much easier/cheaper, so put that micrometer away. I would be surprised if RR would allow you to publish that data or use it for profit though.

I was the manufacturing manager at Walbar Canada in Mississauga Ontario.
We made all 17 stages of compressor blades and vanes for the RB 199 engine.
the information you are looking for is proprietary. The parts were made from 6.2
and 6.2.4.2 titanium as well as Nimonic 90.
We worked to blueprints for part dimensions and mylar charts for the airfoil shapes.
In 1981, MTU started using Catia to design
blade profile geometry. This allowed me to pursue purchasing Catia's CAD/CAM software. We installed the system in November 1983 and produced the first blade shape using the CAM software which was sent to a Bostomatic CNC machine via floppy disc. That's how computer aided machining was introduced to the world.
It cut our airfoil shape development time down to 3 days from one the usual month or more..All the big automakers and Boeing came in the Plant to see the system in operation as well as Sally Ride from Nass.
If you want I could give you the names of 2 design engineers involved from day one.

Thank you for the answer, Rob! And don't let comments that this does not answer the question disparage you. The answer is easy to deduce from the information you have provided.

Buy a book called "The Jet Engine"

It is on amazon. Written by Rolls Royce.

Also we used to scan profiles on a LK

Contact Dave Long at UTC

Or Steve Hotchkiss ..owner of company called Avantec. They know a lot about airfoil and could possibly help you.

Both are on linkedin

You can check it out here (PDF). Good luck.

here, in this pdf file, they told you that they use 65-serie NACA family of airfoils.     http://www.ijedr.org/papers/IJEDR1301005.pdf

Hi David, welcome to Aviation.SE! Please consider including a portion of the linked content in your answer, to help others quickly find the information they need and preserve that information in case the link is broken in the future.

Those old NACA airfoils are not even close to real compressor blades. Compressor airfoils have much more camber and are thinner.

@David thank you for the link. However, I agree with Peter in that these profiles do give a good representation of aircraft wings, but are not suitable for compressor blades.

This is not easy. The quickest way is to google for pictures of compressor flow CFD results, like the one below. The full resolution picture can be found here.

Generally, these rules apply for compressor airfoils:

They should not block the flow path, so their thickness is minimized.
Their angle of attack range is small, so they do not need a big nose radius.
They must produce the maximum flow deflection possible, so their camber is higher than that of most wing airfoils.

The closest thing to a compressor airfoil you can find on a wing is the airfoil of a Fowler flap. Like the compressor blade, it sees almost no angle of attack variation, can be made thin because it is supported every few meters, and needs to produce as much lift as possible.
Note that due to the rotation, any buildup of a thicker boundary layer is prevented by centrifugal forces, which will eject that boundary layer outwards. This allows to use more camber.

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text:
Why is a clock necessary for IFR?
According to FAR 91.205 (d)(6), one instrument required for IFR is:

A clock displaying hours, minutes, and seconds with a sweep-second
  pointer or digital presentation.

Why is it necessary to time things in the cockpit, or know the time?

In Australia at least, a timepiece is required for VFR flight too.

These days we don't worry about that because we can just pull out a phone to see what time it is.

There are several reasons:

For departure clearances. An IFR clearance may have a void or release time so that clearance is only valid between certain times.
For holding pattern legs. A standard holding pattern is based on a time of one minute at or below 14,000' MSL and 1.5 minutes above 14,000' MSL on the inbound leg.
For holding pattern clearances. Holding instructions include an EFC (expect further clearance) time, so that if you have a communication failure while holding then you know when you can safely leave the hold and start an approach.
For timed approaches, where an aircraft is cleared to start an approach at a specific time
For timed turns. A standard rate turn is 360 degrees in 2 minutes, so with only a timer and a turn coordinator you can turn a specific number of degrees.
For en route reporting and general time/distance calculations. Especially in a non-radar environment (i.e. when ATC can't see you on radar) you may be required to give ATC actual or estimated times for passing certain fixes. (This is not strictly IFR only, but it's still relevant.)

All of these scenarios are discussed in detail in the FAA's Instrument Flying Handbook and in the AIM.

Bonus points for digging up the link to the instrument flying handbook (which I was too lazy to do) :)

In IFR the pilot needs to have a second-accurate time indicator for a variety of maneuvers.
For example, the standard holding pattern is 1 minute turns and 1 minute straight legs. Having the number of seconds allows the pilot to fly these maneuvers accurately.

When flying under IFR in IMC you have no external visual references, so there are a number of reasons you may need to time something:

Some approaches require you to be able to time them.
VOR approaches have a table of times from the final approach fix to the missed approach point at a given groundspeed: Since you have no other way to judge distance over the ground you must use the clock.
A "normal" holding pattern consists of one-minute legs with one minute (180-degree) turns at each end.
Turns under IFR are assumed to be made at "standard rate" (3 degrees per second).
If your DG fails you can make "timed turns" with the turn coordinator, a compass, and a clock (30 seconds for a 90-degree turn, one minute for a 180, 2 minutes for a 360) and come out pretty close to your intended course, without being thrown off by compass lead/lag or acceleration errors.

There may be others but these are the ones that spring immediately to mind.

Some procedures require timing, e.g. holding over a fix or NAVAID is usually done in 1min legs. Precise timing is necessary here. Some clearances can also contain a time (e.g. release valid until, revised approach time, etc), where correct timing is necessary.


text:
Can a plane be IFR certified, but not allowed in IMC?
The Evektor Harmony LSA & RV-12 SLSA have all the necessary equipment to be certified for IFR flight, except the only engines allowed for purchase are the Rotax 912 ULS & iS. These engines are not allowed in IMC.
Question: Can these planes be certified for IFR, despite the IMC limitation?

if no, can they be used for training for one's instrument rating and for the instrument rating checkride?
if yes, then if one were to be flown into IMC, would be this be a legal violation or a warranty violation?

Possible duplicate of: http://aviation.stackexchange.com/a/849/167

@SteveV. The link doesn't address the above questions unless I'm missing something. From the reference, "prohibit the use of a Rotax engine at night or in IFR conditions". Does this mean that a Rotax 912ULS cannot be used be used for IFR flight plans in VMC? Can it be used for IFR training in VMC?

The other link answers your question

IFR and IMC/VMC conditions are two independent concepts, and if the aircraft is certified for IFR flight, then you can fly it under IFR.  However, if there is another limitation that prevents you from flying in IMC, then you are not allowed to do so, even if you are allowed to fly under IFR.

The other answer does cover most of this, but it doesn't cover the question about instrument training, does it?

@Lnafziger - Based on the answer provided by rbp it sounds like if there's a limitation preventing IMC that it would not be possible to get an IFR certificate for the plane.

@jt000 Nothing in his answer actually says that...  It says IF it is not type certificated FOR IFR flight....

Why aren't those engines allowed in IMC?

Question: Can these planes be certified for IFR, despite the IMC limitation?
No
Refer to  FAA Order 8700.1:

B.  Type Certificate Data. Appropriate type certificate data will
  indicate whether the aircraft meets the requirements for IFR
  operations.
(1) Section 91.9(a)prohibits aircraft operations without compliance
  with the operating limitations for that aircraft prescribed by the
  certificating authority.

if no, can they be used for training for one's instrument rating and for the instrument rating checkride?
Yes, as per FAA Order 8700.1:

9.  USE OF AIRCRAFT NOT APPROVED FOR IFR OPERATIONS UNDER ITS TYPE CERTIFICATE FOR INSTRUMENT TRAINING AND/OR AIRMAN CERTIFICATION
  TESTING.  The following paragraphs are intended to clarify the use of
  an aircraft not approved for IFR operations under its type certificate
  for instrument flight training and/or airman certification testing.
A.  IFR Training in Visual Meteorological Conditions (VMC). Instrument
  flight training may be conducted during VMC in any aircraft that meets
  the equipment requirements of part 91, 91.109 , 91.205 , and, for an
  airplane operated in controlled airspace under the IFR system, 91.411
  and 91.413 . An aircraft may be operated on an IFR flight plan under
  IFR in VMC, provided the PIC is properly certificated to operate the
  aircraft under IFR. However, if the aircraft is not approved for IFR
  operations under its type certificate, or if the appropriate
  instruments and equipment are not installed or are not operative,
  operations in Instrument Meteorological Conditions (IMC) are
  prohibited. The PIC of such an aircraft must cancel the IFR flight
  plan in use and avoid flight into IMC.

For example, you can obtain an Instrument--Rotorcraft in an R44, even though its not legal in IMC.

Although the R44 IFR Trainer was designed for instrument flight
  training, it is not approved for actual IFR operations. While student
  pilots are flying on instruments, the instructor must act as the
  safety pilot and operate only under VFR conditions.

if yes, then if one were to be flown into IMC, would be this be a legal violation or a warranty violation?
This would be a legal violation of 91.9(a)

91.9(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating
  limitations specified in the approved Airplane or Rotorcraft Flight
  Manual, markings, and placards, or as otherwise prescribed by the
  certificating authority of the country of registry.

Regarding the flight training, I wouldn't be able to do all my instrument training in a non-IFR certified plane, since at some point I'd have to file an IFR flight plan (which wouldn't be allowed unless IFR certified), right?

wrong. you can file an IFR flight plan for training purposes so long as the aircraft meets the regs and you remain VMC

Interesting... Would I put "Training flight, VMC only" in the remarks section for this or just mention it when opening?

they're not under any obligation to keep you in VMC if you're on an IFR flight plan. that's your responsibility, so don't file unless you're sure you can maintain VMC throughout the flight. As it says in the answer, you must have a IFR-rated pilot acting PIC.

That makes a lot of sense. I assume it would be pretty bad form to cancel IFR if they tried to route you into IMC. In Seattle winters, you're almost always 1000' below ceiling, so I could see this being a common occurrence if one were to attempt this out there.

You are PIC. You can cancel anytime you want, so long as you can maintain VFR. In fact, canceling as the weather deteriorates in the direction of flight and turning back towards VFR puts less load on the controller and he'll be thankful to get a bug smasher off his screen. Its much harder the other way around, flying VFR and asking for a "pop-up" IFR clearance puts more, unexpected workload on a controller, and it can take a few minutes before he has time to get you into the system.

True. I'm just thinking of the case where you file & open IFR, then their first route brings you into IMC and you immediately close. In that case, it would be better if you could somehow preface the opening of the flight plan only if VMC is possible from ATC's point of view to save them some work. But I get your point. Thanks!

None of your quotes prohibit the aircraft from being certified for IFR flight, which is what the question is about.  You are correct that if it were not certified though that it could not do it.

Yes, what Lnafziger said.  Good info, but the opening paragraph under "No" completely whiffs on the IMC piece...

@jt000 ATC is starting to get used to it with the proliferation of LSAs now being used for IFR training. But they’re under no obligation to on to keep you in VMC; it’s your obligation to unable/cancel if their instructions would put you into IMC.


text:
Is AVTUR the same as JP-1 fuel?
I read on Wikipedia:

JP-1 was an early jet fuel specified in 1944 by the United States government (AN-F-32). ... It was also known as avtur.

Is AVTUR the same as JP-1 fuel, and the term "AVTUR" is just a nickname?

AVTUR stands for AViation TURbine Fuel and is equivalent to JP-1, at least in the UK.  This might help.

@Simon maybe post that as an answer?

Hardly seems worth it, but OK.

AVTUR stands for AViation TURbine Fuel and is equivalent to JP-1, at least in the UK and in as much as JP-1 no longer exists.  I believe that the US military equivalent is JP8 which is Jet-A1 with additional additives, which differs from commercial Jet-A only by a lower freezing point.
Here is the relevant NATO Def Stan (Defense Standard) for Avtur with is the same defstan as for Jet-A1.
This link to an Exxon document gives a great deal of information for various aviation fuel oils.
[EDIT]
From here:

JP-8 is the military equivalent of Jet A-1 with the addition of
  corrosion inhibitor and anti-icing additives; it meets the
  requirements of the U.S. Military Specification MIL-T-83188D. It is
  the dominant military jet fuel grade for NATO airforces. The UK also
  have a specification for this grade namely DEF STAN 91-87 AVTUR/FSII
  (formerly DERD 2453). NATO Code F-34.

I suspect this answer is confusing JP-1 (which is obsolete and no longer used) with Jet A-1.  The military kerosene-based jet fuels are JP-5 and JP-8, while JP-4 (the old USAF jet fuel) is a wide-cut fuel...

@UnrecognizedFallingObject That wasn't my intention and I've re-read the answer.  I can't see where the confusion is. Please point it out to me.  Thanks.


text:
Is a biennial flight review valid for any airplane category?
If I do a biennial flight review (BFR) in a glider, does it also satisfy my BFR requirement for powered flight (ASEL)?

Yup, sure does.

@acpilot Any source for that? FAR 61.56 Says that "A review of those maneuvers and procedures that, at the discretion of the person giving the review, are necessary for the pilot to demonstrate the safe exercise of the privileges of the pilot certificate." It may be hard to demonstrate power on stalls or other powered aircraft maneuvers in a glider... Not saying I doubt you, but there must be some precedent there...

Yes.  61.56(c)(1) calls for "an aircraft for which that pilot is rated."  The reg does not require a review for each category/class.
And as further confirmation, AOPA's Pilot's Guide to the Flight Review specifically states:

The satisfactory completion of a flight review allows you to exercise
  the privilege of pilot in command in all categories and classes of
  aircraft on your pilot certificate.

Considering that I have never heard anyone say something to the effect of, "well, I just did by BFR for powered, but I still need to take care of glider" I would think that this is highly likely to be accurate.

Interesting; I would feel uncomfortable in relying on this BFR in a glider to get back into a powered airplane or helicopter after a year plus of not flying then, if you held certificates and ratings in these aircraft as well, despite the fact that 61.56 allows for it.

Keep in mind that many "rides" count.  So for example, if you take a commercial glider flight test, that counts towards your flight review applicable to rotorcraft.  This is different, in that you might not already be rated for glider.


text:
What is the effect of opening airplane bay doors on the radar cross section of the airplane?
How does opening airplane bay doors (especially in the case of bombers), increase the radar cross section of the airplane and make it more visible to the radar?

These are usually combined with active measures such as carefully planning all mission maneuvers in order to minimize the aircraft's radar cross section, since common actions such as hard turns or opening bomb bay doors can more than double an otherwise stealthy aircraft's radar return

Source

This is too broad: What type of bay doors? How big and how do they open? How high does the aircraft fly? Is it pitching or banking to any direction? How close to the radar installation(s) is it flying? Is the radar monostatic, bistatic or multystatic?
Generally, determining the RCS of a target and the factors that can affect it, is not an easy task.

Bay doors used for dropping bombs by bombers
How Big? Consider any normal modern bomber
How high? I have not mentioned that because of the fact that wiki article mentions increase in radar cross section without mentioning altitude (and thats why planes use very high altitude to avoid detection)

Your comment reference a Wiki article, yet your question does not. If you want people to take that article into consideration when answering the question, you may want to provide a link and mention the bits you feel are relevant.

Included the source :)

Radar waves are sent back to the radar by two mechanisms, reflection and diffraction.  Opening a bay door may present a surface that is angled such that waves will be reflected to the radar.  As for diffraction, low observable (stealth) aircraft are designed so that a radar wave encountering the aircraft's skin will travel along the skin and be gradually absorbed.  Opening the bay doors creates a break in the skin, causing waves on the skin to diffract.  Some of the radar energy is returned to the sender.
For an amateur looking at "stealth" diffraction is often not accounted for.

The radar cross section (RCS) of an object does not depend on its size, but on the number and orientation of its edges. Opening weapon bays will break up what was a single surface before into several, and the need to align the doors with airflow will create a new edge orientation which will result in a new reflection spike where none was before.
Depending on the direction at which the radar is looking at the aircraft and the RCS of the plane with closed doors, the difference is between zero in the direction of the main reflection lobes and several orders of magnitude in the new edge direction, namely sideways.

In addition to creating a surface that could better reflect radar and breaks that can diffract the radar, the interior of the bomb bay is exposed. The exterior skin of stealth aircraft is specially treated to reduce radar returns, so the untreated interior of the weapons bay and bay doors will also create a much larger radar return than even the exterior surfaces of the open doors.

Assuming, of course, that the bomb bay interior is not treated in radar absorbing material. Not saying that any current stealth bombers are or should be, just that it could be done.

@FreeMan - with the associated cost of added weight of the extra layers, which would only be necessary when the doors opened and which would mitigate a tertiary effect on radar signature with the bays open.

@KeithS … and only help after the weapon has been released. The biggest RCS contribution is most likely the weapon, not the bay interior. And with weapon release the aircraft will give away its position anyway.


text:
What kind of valves are used to prevent flashback in turbine engines?
In a college experiment with Small Turbine Engine, we were told about the use of Valves for preventing flashbacks in engines. What are the available valves used for preventing flashbacks and what are the pros and cons of using different kind of flashbacks?

VERICOR POWER SYSTEMS has a patent for these valves, number US 6357216 B1 and title Flashback control for a gas turbine engine combustor having an air bypass system
The patent includes the following image:

SUMMARY OF THE INVENTION
An object of the present invention is to provide for a control and method for arresting flashback in a gas turbine engine combustion system having a venturi for delivering a mixture of air and fuel to a combustion chamber and a valve for controlling the amount of air flowing to the venturi.
The present invention achieves this object by providing a flashback control system and method having a flashback detection routine, a valve position trim routine, and a reference flame temperature adjustment routine. The flashback detection routine detects a flashback in the venturi by comparing the temperature at the venturi to the temperature of the air entering the valve. The valve position trim routine receives this flashback signal and in response causes the valve to open until the flashback is arrested. Finally, to prevent the flashback from recurring, the reference flame temperature adjustment routine adjusts a reference flame temperature in the control system so as to prevent the valve from returning to the position at which the flashback occurred.
These and other objects, features and advantages of the present invention, are specifically set forth in, or will become apparent from, the following detailed description of a preferred embodiment of the invention when read in conjunction with the accompanying drawings.

The patent can be viewed here on Google patents list, however, it has expired.

Are there any other options or this is the only one in use?


text:
Which engines are Jet-A used in?
Is Jet-A used in turbojets or is it just used in turbofans, turboprops, and the SMA SR305-230 for Cessna?

Why do you think there should be difference between turbojet and turbofan? They are almost the same.

I thought the military might use something different because power is better than efficiency in that line of work.

Most military aircraft have turbofans as well. Including fighters. True turbojets are extremely rare these days. Plus for military having just one stock to supply is much bigger asset than any gain in performance specially tuned fuel could bring.

Jet-A is mostly for turbine engines in general. Turbine engines can be fueled with nearly anything that you can spray over an open flame and will burn.
It is not a substitute for avgas, for the same reasons that diesel is not a substitute for petrol. You can fuel a diesel engine with Jet-A under some circumstances.

Normal diesel engine won't run very well with Jet-A1, but it is possible to build one for use with Jet-A1 (or any other specific jet fuel type, but Jet-A1 is most common in Europe) and such engines are used on some new aircraft especially since avgas is heavily taxed in Europe.

"Turbine engines can be fueled with nearly anything that you can spray over an open flame and will burn."  With one partial exception - they generally don't take well to fuels with solid combustion products (since these deposit on the turbine blades and do bad things to the engine), unless the engine burns hot enough to keep the exhaust temperature above their vaporisation point until well past the outlet.

Jet-A/A1 is used by pretty much all civilian turbine aircraft. The US military use JP-8 which is similar but with extra additives in pretty much all their aircraft.
The fuels can also be used in suitably designed diesel engines. AIUI the US military runs pretty much all it's vehicles off JP-8 and some airports use Jet-A/A1 for their ground vehicles. In both cases the motivation is simplified fuel handling.
Due to cost/availability/environmental concerns with avgas there has been a push to develop aviation diesel engines that run on jet A/A1 (and in some cases can also run on automotive Diesel). However the GA market is relatively small, certification costs are high and making a Diesel engine light and reliable enough for aircraft use is not easy. So-far only a small proportion of piston aircraft have Diesel engine options available.


text:
Where are the first structural damages after maximum speed is passed?
What 2 parts of the airframe are the first to have structural failure after exceeding maximum speed?
Sorry. I just thought there might be a part that usually failed first.

This is very specific to each aircraft design, and will vary from airplane to airplane...  It would also depend on the configuration of the airplane.

As Lnafziger points out it's hard to really answer this generically. If you exceed Vfe we can presume you're going to damage the flap mechanism. If you exceed Vne you could lose a control surface to flutter, oilcan/damage wing skins, overstress a wing spar (or attach bolt), or any number of other things - where the weak link is depends on the aircraft...

This is a very broad question and can not be answered specifically. It also depends on the attitude / configuration when exceeding Vne, including other factors as mass / balance, age of components and already existing damages. Obviously there is a safety margin, but in certain cases (eg when having a load factor) this is not enough. It is very common to have nearly invisible cracks in the structure after reaching various limits, but especially at the very high speed flutter can happen. As said above, this question cannot really be answered, as it is quite broad.

No need to be sorry ptgflyer.  You got your answer this way, it just wasn't what you were expecting!  :)

Q: Which link of a chain will fail first when you exceed the maximum design tension?
A: The weakest link.
It could be any link since none is designed as the weakest link.

or you just crash when the plane reaches transonic speeds and control is lost

Unfortunately it's impossible to answer your question. No part of any aircraft design will simply fail because the 'speed' is to high. You need to consider the airspeed (in this particular case the equivalent airspeed) as a force acting on the airframe and as Force stated correctly it's not the only factor, which needs to be considered. Mass, existing weakening of the structure and the attitude as well as the surface design, which obviously varies between different aircraft, need to be taken into account.
Now tell a Pilot that he is not allowed to bank more than x1 degrees,  if the aircrafts mass is bigger than x2 or even lighter than x3, if the aircrafts last overhaul was more than x4 month ago, at a higer airspeed then x5 KEAS. He will refuse it - by the way the aircraft won't be certified because of its manual - as well as he would refuse to calculate the load factor while flying. Thats why maximum speeds are calculated or even set up during flight testing. VNE, VA, VFE, VLO... all expressed in KIAS. By the way 2 different aircraft flying the same KEAS will most probably don't have the same indicated airspeed.
In general you can say that at maybe 70 percent of all aircraft either the parts which carry the heaviest loads or those parts which are not reinforced to withstand high loads, because they don't have to during normal operation plus safety margins, fail first when exceeding VNE and the safety margin in straight and level flight.
The never exceed speed can also be set as the aircraft becomes only very hard to control above it, there were no further tests and calculations made or for sure also some other reasons.

I'm not sure I understand - you say it's impossible to answer, but your actual reply seems to try anyway. If you think this question is too broad, you should vote to close it and leave a comment as to why.

authors: Vladimir F Героям слава


text:
Is it possible for a plane to use cameras and screens instead of a clear windshield?
I was just wondering: is it possible to have a commercial plane with no cockpit windshield, just external cameras and video screens?
The question come in my mind after reading the nth occurrence of laser in pilot's eyes. Moreover, a structure without windscreen is surely lighter: when there are not passenger, we avoid to put windows! Which are the limits and the opportunities to this solution?
With "ever" I don't mean "in centuries" but in 30/40 years.

I am sure such idea was already mentioned several times here. Technically, it is completely possible. However, it has significant problem. It adds a point of failure and nobody wants to add that.

It's been done in testing before

@fooot oh, it is very interesting! That's what I meant. I will spend sometime online for some researches. Thank you.

@fooot I don't think there was any visibility from the aft cockpit. It was mainly to test IFR, so that was not considered a problem

Preventing laser attacks using aircraft without windows is like preventing burglary by building homes without windows: It's not a solution. A good solution would be to have kW-lasers onboard which fire automatically on the source in an act of self-defence.

Slightly off-topic, but the Spirit of St Louis has no windscreen but rather a sideways-oriented periscope, and many drone aircraft use cameras for obvious reasons.

@aeroalias some of the tests did include various video and sensor feeds that could be displayed in the aft cockpit.

@mins I don't see that as a solution to the current laser problem. If we were talking about some kind of weapons-grade laser attacks maybe. But I think most of the laser incidents are not so much attacks on the plane but just stupid people who don't know or don't care how reckless it is. I can see those same people being even more motivated to do it if they can trigger a response from the aircraft.

@TomMcW: Just a joke. By kW-laser I meant a power in the order of magnitude of the kW. That should be enough :-)

@mins Smoke 'em where they stand!

The biggest problem is depth perception, without the ability to adjust the view based on the position of the observer, its going to be difficult to judge distances. This will be especially confusing since the camera is not in the same location as the pilots head, making it hard to translate it to a 1:1 eye:camera system and having the perspective in a different position than the pilot(s).

@TomMcW: Re "stupid people", think of it as improving the gene pool :-)

@mins Like this?

In practice they would use VR goggles. The technology is mature enough that it is expected to hit the consumer market within a year or two. And it has the issues with depth perception and lag already solved (more or less). And it would probably be used only for remote controlled aircraft. Maybe for supersonic optimized military aircraft even with a pilot, but hard to think of an use case that would require carrying a pilot for such.

@HCBPshenanigans While that would get the job done, I'm pretty sure that is a megawatt class laser. :) One of the tracking lasers from that could work, though.

Some cons I consider obvious are: the much lower dynamic range of camera/screen systems, low resolution, delay of about 30milliseconds, and cameras are susceptible to laser attacks as well (in fact might already suffer from a flight heading towards the sun for a few minutes)

@reirab Go big or go home.

@VilleNiemi Oculus Rift has already had dev kits out for a year or so and consumer version releases this summer, IIRC. Also, Google Cardboard has been around for a year and a half.

@reirab Yes, I know. That is why I am optimistically assuming something useable to be on the market within a year or two.

Is it possible? certainly yes. Airbus has applied for a patent for a windowless cockpit in which the external view is displayed in the cockpit using cameras and screens. The technology itself is available and some significant progress has been made in recent years in the related equipment.
Will it become a reality? Maybe. At present, there is nothing wrong with windshields in aircraft (pointing laser at aircraft is illegal; anyway, lasers can damage camera sensors too). Why fix something that ain't broken? In the future this may well be used, maybe in supersonic aircraft (For example, spike aerospace has proposed a design without cabin windows; interestingly, the design still has cockpit windows). Addition of cameras and displays adds one more layer of complexity, which is at present unnecessary.
Also, there are other issues to consider. In order to give the pilot with a view at least as good as the exiting aircraft, images from multiple cameras have to be 'stitched' and displayed. The system should be able to do this without any lag (F-35 had a similar problem while joining feeds from its DAS). Unless there is a compelling reason for the addition of cameras and displays, the windscreen is here to stay.

"The system should be able to do this without any lag" There are studies about how much "lag" a human can notice and that's not even "can't compensate for", IIRC it's around 60ms which in computer time is eternity these days. I highly doubt that joining static cameras onto a static display was the problem, it was probably the fact that the displays on the F-35 were not static. Also the F-35 uses very old computer technology.

One reason to do this would be that windshield are expensive (>$20K) and have a fairly high failure rate, in my experience #1 windshields last about 6 years at a commercial airline. They are also very heavy. They create a weak point in the fuselage requiring heavier structure and usually force a less than idea aerodynamic shape. So there are reasons other than laser pointers to do it.

@Sam, I am not sure what the lag is, but I know that lag in video causes issues on KC-10 refueling operators. Basically there is enough lag to cause the operator to start pilot induced osculation. I know there was a lot of work on the KC-767 and KC-46 remote aerial refueling stations to remove as much lag as possible, which of course is easier with today's technology. The other problem with remote aerial refueling operations is the loss of depth perception.

Well I hope they don't get that patent then! Clearly the NASA plane has already done this before so it's not a new idea.

@Sam Around 60 ms? Are you suggesting that a human wouldn't notice a 17 FPS frame rate? If so, I know a lot of gamers who will adamantly disagree with you.

@reirab - 60ms latency, not a 60ms refresh cycle.  You're seeing things 60ms after they happen.

@reirab, that is not at all what I am saying. Latency and refresh rate have nothing to do with each other.

60ms may seem like an eternity in computer time, but a lot of digital video systems work by having a camera capturing 60 frames/second (start with 16ms of latency from one frame to the next), wait for an entire frame to be loaded into RAM before starting processing on it (which may be another 15ms), then do some processing, and then start feeding it to a display (which could be another 15ms).  If the input and output frame timings aren't synchronized, that could add another 15ms to the mix.  Pretty sad considering that old analog video had a 17ms worst-case latency for fast motion.

It's entirely possible to do this now, it's simply not a good idea. The drawbacks to safety outweigh the benefits of doing so. If you have no cockpit windows an electrical or systems failure would leave pilots totally blind, without any references whatsoever. The "mark I eyeball" works in a wide variety of conditions and does not require electrical power of any kind. Plus, there's usually 4 of them in the cockpit, and chances are at least one of them will work.

With modern fly by wire systems, doesn't a total electrical system failure result in loss of control anyways?  If a windowless cockpit was implemented, it would likely have the same number of redundancies as other essential flight systems.

Misleading visual cues is major cause of incidents. Relying on vision didn't prevent the Grand Canyon Crash 1956. OK argument for slow moving civil aviation but gains as much you lose for passenger airlines.

@RockPaperLizard The power supplies for it could be equally redundant, but it would be hard to make the screens themselves equally redundant while preserving their position. Also, placing redundant cameras close enough that they are capable of producing the correct field of view and also far enough apart that they wouldn't be likely to get taken out by a single event (e.g. bird strike) could be tricky. Doubly so if that single event is something like icing or a hail storm.

@reirab Those are good points.  I'm not sure they are insurmountable, but good points nonetheless.

@user2617804 Your comments are true.  It makes me wonder how we can envision the cockpit of the future assuming pilots could not directly view their surroundings.

@reirab - I can't say I agree about the camera proximity thing. Post-processing need not introduce significant latency because the transformations and deformations are a function of relative position and angle; for predetermined camera positions and angles the transformation matrix can be precomputed and applied in hardware by an FPGA. This depends on having fixed cameras, so you'd have to have lots. Good cameras these days are cheap, small, light and low power. You wouldn't put a fixed camera in a dome, you'd set it behind a pinhole in the aircraft skin. Low drag.

@PeterWone That's normally used for 3-D rendering. Seeing the world with cameras, making high-resolution 3-D models from the flat images, creating the correct textures for the faces, and then rendering the scene and projecting back into the appropriate 2-D views is non-trivial. It's not impossible, but it's not easy. You'd probably want something more like a programmable GPU (or several programmable GPUs) than an FPGA. Doing that fast enough to maintain a usable latency for a vehicle whose most important out-the-window views involve racing through the scene at 200 mph isn't easy.

@PeterWone At any rate, windows are much cheaper and have far fewer likely failure modes. It's also worth noting that using screens to emulate the windows assumes a fixed viewing position... which is a bad assumption when you have 2 (or more) pilots who need to be able to look at the same part of the glass and see two different images based on their position relative to the glass. An Oculus-style wearable headset for each crewmember would probably be a better solution.

Why correct the camera image to the "proper view"?  I would think in many cases the eyeball view from the cockpit would really not be the ideal, but people tolerate it because they'd rather sit in the cockpit than on the outside of the aircraft.  Certainly adding additional cameras would be helpful in many cases (e.g. avoiding mid-air collisions in cases where at least one plane lacks ATACS and each plane happens by chance to stay in the other plane's blind spot).

That should be ... exciting ... during an electrical failure.
Good luck getting it approved for use anywhere in the world, you can't even build a pure glass cockpit in many jurisdictions. Likewise you can have all the cameras you like provided you can still look out the window.
It's certainly technically feasible but it's not a good idea.

Somewhat, but the lack of depth perception may be an issue on the taxiways.
But if lasers is the concern, I think they should install something similar to the auto darkening lenses used by welders to the front windows.

You could at least reduce, if not completely solve, this problem by using VR headsets (e.g. Oculus Rift.) You could even attach cameras to the headset itself and have the system programmed to display the cockpit interior except when the pilot is looking where the windows would otherwise be.

Technically possible but not very comfortable. As a first step, windowless passenger aircraft could be attempted. In crowded Indian buses with windows being swamped by opaque advertising material it is very disconcerting not knowing where you have reached. Passenger experiences can be taken as a starting point. Also the experience of astronauts could be considered....


text:
Is there an online source for Canadian Instrument Approach Procedures?
The FAA offers instrument approach procedures on their website free of charge, and EASA does too.  Does Canada have them online for us to use?

Not officially, no. The official approaches are available in a PDF format to download for 20 CAD for each volume.
However, FltPlan.com claims to provide free, up-to-date charts:

In cooperation with Nav Canada, FltPlan.com is pleased to announce
  free Canadian Approach Plates, also know as CAP (Canada Air Pilot).
  These online charts include all instrument approaches, airport
  diagrams, SIDs, STARs, and special use approach plates for Canadian
  Airports. They work similarly to the already available U.S. approach
  plates.
CAP is an extension of FltPlan.com's continuously expanding coverage
  of Canada, Mexico, Latin America and the Caribbean. In May of this
  year, we expanded our coverage to include the filing of IFR
  intra-Canada flight plans. The availability of free, online Canadian
  Approach Plates brings a new level of safety and convenience for
  pilots in the planning stages of their trip.

Though I have not seen anything from Nav Canada stating that this is "in cooperation with Nav Canada", they do seem to be an authorised distributor of paper charts.
Note FltPlan.com warns that these charts shall not be printed as a replacement for "proper" paper charts -- I am not sure whether these are deemed to be official or not, but it is rather unlikely.

There is currently no official source of free Canadian Aeronautical Publications which can be printed for use.


text:
When flying a circling approach, is it permitted to begin the visual circling segment prior to the final approach fix?
If it were a beautiful sunny VFR day and you were cleared for a circling approach, can you begin the circle prior to the final approach fix/circling DH in order to maneuver visually to land?
Here are two examples of situations where it would be very useful, and both are real life clearances that I have gotten multiple times:

Example 1 - KASE
Clearance:

N1234, Cleared for the VOR/DME-C approach, cleared to land runway 15

If you follow the step downs until the final approach fix (ZIGBU) you will be at 2,983 ft. above the runway (10,820 ft. MSL) with 2.9 miles to go (9.61 degree descent angle).  To put this in perspective, on a normal 3 degree descent, you should be at 870 ft. above the runway so are over 2,000 ft. high on less than a 3 mile final.
Could you begin the circle early and descend while visually avoiding any obstacles prior to the step-down fixes?  Say cross ALLIX at 11,000 ft. and ZIGBU at 9,000 ft. (assuming that this cleared all obstacles)? Keep in mind that this is a circling approach so we will be operating below the MDA visually at some point on final anyway.
If not, then it would be nearly impossible to land straight-in while flying most jets, and yet I have never seen anyone do a 360 or a similar maneuver while on final here (and who would want to do that in the valley anyway??).

Example 2 - KTEB
Clearance:

N1234, Cleared for the ILS Runway 6 Circle Runway 1 Approach, cleared to land runway 1

If I fly the ILS (localizer and glideslope) until reaching circling minimums, especially in a category C or D airplane and with this runway layout, it will take a lot of room to turn right for a base leg to runway 1 and then turn back left to intercept final and lose the required altitude.
Could you start the circle a little sooner by making the right turn early (prior to DH, but still within the protected circling area) in order to intercept the extended final for runway 1?

Not really relevant to the question, but couldn't you just ask for a visual approach in that case?

@roe You can if you have the airport in sight. And request it.  And it is approved.  That's actually what I usually do but I never hear anybody else do that so I have to wonder what they are doing. In any case, I'm just wondering about the different methods available to fly this legally and without surprising ATC.

While researching this subject, I found a few things that shed light on the subject:
Procedures
FAA ATC Order 4-8-1 Note 1 says:

1. Clearances authorizing instrument approaches are issued on the basis that, if visual contact with the ground is made before the
approach is completed, the entire approach procedure will be followed
unless the pilot receives approval for a contact approach, is cleared
for a visual approach, or cancels their IFR flight plan.

So we have to follow the entire approach, which includes all mandatory altitudes.
Aspen Approach
AIM 5-4-20. Approach and Landing Minimums says:

c. Straight-in Minimums are shown on the IAP when the final approach
course is within 30 degrees of the runway alignment (15 degrees for
GPS IAPs) and a normal descent can be made from the IFR altitude shown
on the IAP to the runway surface. When either the normal rate of
descent or the runway alignment factor of 30 degrees (15 degrees for
GPS IAPs) is exceeded, a straight-in minimum is not published and a
circling minimum applies. The fact that a straight-in minimum is not
published does not preclude pilots from landing straight-in if they
have the active runway in sight and have sufficient time to make a
normal approach for landing. Under such conditions and when ATC has
cleared them for landing on that runway, pilots are not expected to
circle even though only circling minimums are published. If they
desire to circle, they should advise ATC.

The key part for this discussion is that, for approaches that would be straight-in if it weren't for the high descent rate on final (like the KASE approach), pilots are not expected to circle even though only circling minimums are published. If they desire to circle, they should advise ATC.
Well, in this case we can't land straight-in after making the last crossing restriction, so what can we do?
Combining the two quoted passages, our options are:

Get approval for a contact approach
Get approval for a visual approach
Cancel our IFR flight plan
Get approval to circle since we can't land straight-in.

The first three are pretty straight-forward and can be used if you pick up the airport visually in time.
If you need to circle, I found a great article called Circle-To-Land Tactics which was written by a former chairman of the ALPA TERPs committee.  He suggests overflying the runway and then flying a modified pattern:

Teterboro Approach
We can't start our circle until we are within the protected circling area.  This means that for my category C airplane, I have to wait until 1.7 NM from the runway threshold before I can begin my turn.
We could make a right 90 degree turn followed by a left 90 degree turn to line up on final, but that would eat up about one mile just by turning.  Since runway 1 is actually closer to us than 6 at this point, I have even less distance to work with and can't even see the runway during the first turn because we are banking the wrong direction.  This would be pretty tight.
In this case, the previous article recommends a circle like this (which would be modified for our actual runway layout):

In good visual conditions, I would just ask for a visual approach so that we can start the turn a little sooner and land "more" straight-in without flying all over the airport.

One last point:  Since there is a control tower at both of these airport, make sure that they know what we are going to do!

Well, some of the things you are talking about are not even permitted for a visual approach :-)
Here's my 2c :
ICAO Doc 8161 7.2.2

After initial visual contact, the basic assumption is that the runway
  environment should be kept in sight while at minimum descent
  altitude/height (MDA/H) for circling

The circling approach allows you to fly at/below the MDA around the airport while having (part of) the airport in sight AND while inside the circling approach area (~4.5 miles max for category E). It's not a license to disregard altitude restrictions while descending on the approach. It's also not a license to start flying around the class D airspace at will.
For KASE the highest category allowed for circling is C. The protected area (centered around the runway threshold) for category C is 1.7NM.  You cannot begin your circling until 1.2 NM after ZIGBU.
Note that after ZIGBU you can descend to the circling MDA of 10220 and with the airport in sight you can continue to descend all the way to the rwy threshold any time you wish. How are you going to lose 3000' in 2.9 NM I have no idea. But I'm pretty sure a circle to land clearance does not allow you to break that "10820' or above" restriction.

So what wouldn't be allowed during a visual approach?  You don't have to even tune in an approach procedure when cleared for the visual, much less follow published minimums...

that was more of a tongue-in-cheek reference to the comments below the question : At the airport where I mostly fly, the clearance for visual approach comes with altitude restrictions. AFAIK, unless otherwise specified, visual approaches have two restrictions: noise abatement are still in effect, and no exiting of controlled airspace/radar coverage (below or sideway)

You cannot legally descend below minimum altitudes. Going to 11,000' before Allix or 9000' before Zigbu is not allowed unless you cancel IFR or are cleared for a visual approach. Sometimes the stepdowns are used to keep you above traffic instead of obstacles. That's the case at Orlando International, for example, where the ILS approach from the north overflies the ILS approach from the east at Orlando Executive.

Two things:  1) A precision approach is a lot different than a circling approach (as eventually we will have to be flying around in the approach area below minimums at some point anyway if we are going to land) and 2) You say that it can not be done legally.  Do you have a reference for that?  Thanks!

The underscored altitudes in the profile window of the instrument approach procedure designates a mandatory minimum altitude. If there is no underscore, it is optional. An overscore designates a mandatory max altitude. The 1500 ft. altitude at Teterboro, or example, is both a minimum and maximum -- you have to fly that altitude unless otherwise assigned.

@Lnafziger Re the descent from circling altitude to the RWY:  AIM5-4-7d - “ . . . where a DA/DH or MDA is applicable, no pilot may operate an aircraft below the authorized MDA or continue an approach below the authorized DA/DH unless the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and for operations conducted under Part 121 or Part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing.”


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How can someone get clarification from the FAA on the intent of a regulation?
How does someone request a letter of interpretation from the FAA if a particular situation surrounding a regulation or policy is not clear?

I know you can send a letter to the Office of the Chief Counsel, but not sure about any other way to do so.

Generally there are two ways to get an interpretation of regulations from the FAA.
The first (less-formal) way would be to call or email your local FSDO with your question -- they will usually get back to you pretty quickly with a verbal opinion or an email (on the two occasions I've contacted the local FSDO I've gotten an answer within 1-2 days).
Interpretations from your local FSDO are essentially valid within their coverage area (if you get an opinion from Farmingdale in New York the folks in Los Angeles, California may not honor it).

The second (very formal) way is to write an actual on-paper letter to the FAA's office of the chief counsel requesting a legal interpretation of some specific regulation(s) and mail it to their office:
Office of the Chief Counsel
800 Independence Avenue SW
Washington, DC 20591

This request should be as specific as you can make it, for example:

May the FAA hold a person who performs maintenance on an aircraft responsible for the proper performance of that maintenance under 43.13(a) and (b) when that person was not the person who made the maintenance record entry required by 43.9?

If your request is inspired by some ongoing action (say a warning letter) you should reference it and include a copy to help speed things along.
The FAA's legal staff will chew on the request for a while, and eventually produce a legal interpretation (the linked interpretation, which answers the example question above, took about 5 months, and it is a relatively simple interpretation - The more complex the regulation that needs to be interpreted the longer it will probably take).
Counsel interpretations are organization-wide precedent, and on occasion they can overrule opinions/decisions from a FSDO. They are effective "The Final Word" on how regulations are to be applied (unless overturned in court).

Now there is the RCCB too!


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Why is flutter a function of true, not indicated, airspeed?
I am learning about gliders in preparation for an exam. It says in the textbook I am reading that for a glider, you use indicated airspeed for most relevant speeds (stall speed $V_s$, best glide speed $V_{BG}$ etc). However, $V_{NE}$ should never be exceeded in true airspeed. As far as I can tell, this is because flutter depends on true airspeed rather than indicated airspeed. (Let me know if this assumption is wrong, because that would make the title wrong.)
Why is this the case? Is flutter somehow related to the speed of the air molecules, rather than to the energy provided by them?

Peter, I would like to make a strong recommendation that you change the question title to: "Why is flutter a function of true airspeed?" because you're already correct, at least partially, that it is because of flutter.

@RyanMortensen good point. I will modify both the question and add a comment explaining.

Flutter happens when structural and aerodynamic eigenfrequencies converge. Aerodynamic eigenfrequencies depend on the time the air molecules take to transverse an aerodynamic surface.


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Should I avoid testing unnecessary equipment?
Suppose you are on a day VFR flight and you are testing your aircraft lights. If you discover that the bulb for one of your nav lights is blown, then you can turn the switch off and tape it off, placard it as inop, and fly anyway. However, if you don’t placard it, my understanding is that you are not legal to fly, even if it is day VFR and you leave the switch off.
My question: should you avoid testing unnecessary equipment? Presumably if you did not test the nav lights during your preflight (not intending to use them) then you never knew they were broken, therefore you didn’t need to turn off and placard as inop. What is best-practice here? My question is specifically about nav lights, but I am also interested in other optional equipment (eg an autopilot).
(This is in the USA as a Part 91 flight.)

What is the deal with placarding it? Putting a sticker with "inop" written on it won't take more than few seconds, will it? And at least you know it needs to be fixed, so you don't get stuck next time you want to go flying and actually need it.

The best practice is to pre-flight everything for every flight:

If you have different pre-flight procedures for different situations then sooner or later you'll use the wrong one and miss something that you should have found. Consistency is really helpful in procedures.
Even if something isn't needed for the flight, checking everything gives you an accurate picture of the state of the aircraft. One broken light is probably just a light bulb, but 3 broken lights and inop pitot heat may be a more serious electrical problem. If you don't know the state of the aircraft then you can't make informed decisions.
Plans change. You might set off for a day VFR flight on a clear, sunny day intending to be home hours before sunset. But if the weather changes quickly or you get delayed then your flight home might have to be night VFR or IFR. If you have equipment issues that restrict your options then it would be best to know that before you depart.

There's nothing wrong with flying with inop equipment provided that you know about it, you've complied with the rules in 91.213 on minimum required equipment and deactivating and placarding, and you've made a conscious assessment of the risk. But not inspecting the aircraft properly or deliberately ignoring inop equipment is a really great way to put yourself in an "up there wishing you were down here" situation.
And from a regulatory point of view, if you don't preflight properly then you're probably in violation of 91.103 ("become familiar with all available information concerning that flight") and of course 91.13 ("No person may operate an aircraft in a careless or reckless manner").

Please note that you can't defer everything.  Some items are required by basic regulations, the aircraft type certificate, or the specific operation.

It is the job of the pilot in command to verify the aircraft is in an airworthy state before flight.  If you chose to not test "optional" equipment you would still be illegal if that equipment was inoperative.  You are required to follow 91.213 if that equipment is inoperative whether or not you found out about it.

In the case of a light bulb, who's to say that it wasn't working fine the last time it was used?  Or even that it worked when checked at the beginning of the day, but "now" when turned on, it burned out?  Things work fine right up until they don't...

@Ralph J choosing not to do part of the preflight to avoid finding out about a malfunction is a hazardous attitude.... Invincibility - It won't happen to me.


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How to choose a flight school?
I am considering enrolling in a PPL course, and am getting information about the flight schools in my city (Rome, Italy).

What should I be looking for?
How can I choose among them?
Their fees differ by at least €3000. Are there differences between the schools that justify such different prices?

One reason for a very large price difference could be the aircraft: a newer aircraft with advanced avionics will typically cost much more per hour than an older one with standard instruments. But there could be other reasons too, and it's definitely a good idea to investigate that in detail before making a decision.

If they'll let you, go pay for a lesson with one of the instructors you'll fly with. You need to know whether the program fits your expectations.

@Tim - agreed. I took lessons at 3 different schools w/ 3 different instructors at the beginning of my lessons & found there's nothing more important than a CFI that you can get along with. You'll be in the cockpit with them a lot & under stressful situations. You need to be able to work with them comfortably to get the most out of your lessons.

I'm not sure how it works in the EU as I am an American PPL student but let's ignore the small specifics and look at some general points.
Number of planes
Where I fly there are 2 flight schools; one has a fleet of about 20 planes from Grumman trainers all the way up through a Seminole. The other school has 2 planes... The obvious thing here is down time. The fact is that planes break, need routine checks and get rented by other students. A flight school with more planes (and an appropriate amount of instructors) will be able to handle these issues better. Many times I have booked a plane to find that it's in the shop and I get assigned another plane (same make and model).
Type of planes
While you cant be as picky here since sometimes geography limits you, some schools may be significantly more expensive than others. One of the nearby fields flight schools I looked at had just bought a new fleet of SR22's and were renting them at 250 USD an hour wet compared to the 100 USD an hour wet that I pay for a Piper Warrior. This can make a big difference in cost of training. Not that you are thinking this far in advance but if you do intend to one day buy a plane you may want to consider training in the type although its hard to say what kind of plane you would buy before you start flying :). If you intend on getting your instrument rating (I assume there is an EU equivalent) you will also want to make sure you are at a place that has instrument-capable planes and possibly even a precision approach system.
It also stands to reason that a place with older planes may see more down time as the planes may need more service but most old planes that I have flown are well kept. Here in the US trainer planes need to be inspected every 100 hours so they are out somewhat frequently for that already.
Number of instructors
Here in the US many instructors are doing so to get enough hours for their ATP. With that in mind instructors are subject to leave at any time if they make their hours and find a commercial job. Bigger schools will be able to reassign you to another instructor or may have better luck hiring a new instructor to fill the gap.
Type of airport
Again sometimes you can't be picky here because of geography but training at a towered airport as apposed to an uncontrolled field can help you hone in your radio work from day one. A bigger slightly more busy airport may also give you real experience with things like wake turbulence avoidance. Most larger airports also tend to have 2 runways which can help you on those windy days (depending on direction and such). They also tend to have better services like plowing, precision approaches, fuel (not all airports have gas!), pre-heats that don't take 20 minutes to show up etc. This can also be a but of a curse sometimes as larger airports are subject to traffic and you may find your self sitting on the runway waiting to take off on a nice day.
Cost
This can be a big factor for some people. Some are lucky enough to have the money to fly where its easiest for them (close to home or work) etc., while others don't have this luxury and must fly where its the cheapest. Here in the US a cheap school will still get you the same PPL that a super expensive place with a brand new SR22 will. So if your goal is simply to fly and cost is a serious factor there is nothing wrong with going with the cheaper option (which may involve driving a bit farther) as long as you factor in the potential down time of the planes or difficulty of booking them.

Your question is a nice but at the same time, very broad. It is similar to What to look for in a flight instructor?
I've pointed out some resources which provide very valuable information about the topic. However, please keep in mind that the most important factor is how quickly you can master a particular tasks of flight training. The question I referenced above will answer your next question once you settle down with a flight school.

How To Choose A Flight School / Flight Instructor
How to Choose a Flight School for an Aviation Career
Choose Your Flight School
How to Pick a Flight School

Good luck in following your dream.


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What might this P-68 be doing?
Right now (28 May 2020, 0910 UTC) this Partenavia P-68 is repeatedly flying, alternately, northbound and southbound over Rome, Italy, in regular straight paths about 45 km long, some 400 meters apart. Flightradar24 gives for it just the model (no callsign, not anything). Yesterday morning it was doing the same, for at least six or seven runs.
What might it be doing? Is this the same kind of flight as in this other question? I can't say, since the flight pattern is somewhat differen: for one, the parallel paths there are some 4-5 km apart, while in this case they are less than 0.5 km.

@J.Hougaard: I don't actually know. There are some similarities, but also significant differences: for one, the parallel paths in the other questions are some 4-5 km apart, while in my case they are less than 0.5 km. And since I don't know about this kind of flights, I don't know whether these difference are significant.

Also, Google Earth imagery, the really hi res stuff, is partly based on aerial photography, not satellite imagery.

@DaG No it's definitely the same. Different aerial photography missions are flown at different altitudes and with different distance between tracks depending on the desired image resolution. The goal is the same.

Thanks, @J.Hougaard. The problem is that the existing question&answer doesn't reply in itself to my question, unless one does already know that it does. :)

This question is answered here. It actually appears to be one of the exact same aircraft from the exact same company.    What is the purpose of grid-like pattern route for small aircraft?

Company info here.    http://www.cgrspa.com/en/chi-siamo/la-flotta/

According to the pattern and altitude, this aircraft is probably doing aerial photography or 3D mapping (or both !) for services like Google Maps or Apple Plans.
The Partenavia P-68 Observer is actually made for this kind of missions. According to this link, the Italian State Police uses it too.
Since it's happening over Rome, it could be on an archeological mission too, but that is speculation.

Yes agree, suggest looking up the terms "photogrammetry" and "remote sensing"

Exact same aircraft.  What is the purpose of grid-like pattern route for small aircraft?

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Which design method is used for super critical airfoils?
How is an Airfoil categorized as super critical or not super critical? What are the ways to design a super critical airfoils?

Critical speed or Mach number is the speed at which the speed of sound is locally reached somewhere along the flow around an airfoil. A supercritical airfoil can tolerate operating speeds slightly above the critical speed (hence the name), which means that a pocket of supersonic flow will show up, most likely on the upper surface. What qualifies an airfoil as supercritical is that the recompression does not need a shock, but can be done shock-free for a small lift coefficient range by clever shaping.
See this question for more.
Calculation of a supercritical airfoil is best done with a computer program which models the flow conditions around Mach 1 faithfully. Once such program would be TSFOIL. The picture below shows one result for the BACJ airfoil at Mach 0.8, and you can see that the speed on the upper surface reaches Mach 1.3.

To add to the answer already given by Peter, on how to design a supercritical aerofoil, of coarse now we have many software which can tailor aerofoil shape for required loading curve. But you could do it using experimental method (fine tuning using Wind Tunnel runs) as well. This is one of the ways, although tedious and not the one which anyone would take now, but one of the ways for sure. In fact the first Supercritical aerofoil designed by NASA was through experimentation. Interestingly, supercritical aerofoils are very much what Natural Laminar Flow aerofoils look like. While those aerofoils were proposed in times as far back as 1940's I think, they did not catch the fancy since they were not proved very practical due to difficulty in maintaining laminar flow in real life, they were found out to be useful to push critical Mach number to a higher value.


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How much power is generated by a Ram Air Turbine (RAT)?
For long range, wide body planes A380 and B777, what is the power generated by RAT (Ram Air Turbine)? And which all are the systems which the RAT drives?

This will vary substantially between aircraft. It is better if you zoom it in on one model despite there then being several questions.

editted the question to two aircrafts

According to the Flight Crew Operations Manual of the Boeing 777:
Hydraulics

The RAT, when deployed, provides hydraulic power only to the primary
flight control components connected to the center hydraulic system.

Which leaves out:

Nose gear
Main gear
Steering
Brakes
Flaps
Thrust reversers

Electric
The RAT powers both C1 TRU and C2 TRU, which powers the captain's and first officer's flight instruments, respectively.
The RAT can supply electrical and hydraulic power simultaneously. However, if the RAT is unable to maintain its RPM, the electrical load is shed and provided by the main battery, until RPM is satisfactory.


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What are the requirements to convert a license from Iran to USA?
What is required for someone who has CPL, IR and CFI licenses from Iran to fly in USA? What is the requirement to convert license?

You cannot convert the CPL to FAA-CPL. What is possible is to obtain a FAA-PPL certificate by verification of the your current foreign license. This certificate will be valid as long as your foreign license is (plus medical conditions, and 24-months PPL flight review required for any PPL in the US).
With the PPL certificate, you will be able to obtain IR and CPL:

Pass IR and CPL written tests.
Attend training for IR and CPL practical checks.
Accumulate at least 250 flight hours. Time in the foreign country with the foreign license will count as well, but at least 3 hours are required with the FAA instructor. The instructor will vouch for the candidate is ready for the check-ride.
Pass CPL and IR practical checks.

A valid residence permit will be necessary to use the FAA-CPL.
The CFI roadmap is similar, written tests and checkrides are mandatory, there no minimum hours to be flown in the US. As a large part of the knowledge required is similar to many ICAO-member countries (teaching, meteorology, navigation, aerodynamics, etc) this shouldn't be a problem to be certified FAA CFI.

Related:

Do I need a PPL license for a CPL license?
I have a European EASA license - what do I need to do to be allowed to fly in the US?
Can a pilot with an ICAO Multi-Crew Pilot License fly an airliner into the U.S.?

References:

Required knowledge FAR 61.123 et seqq.
Required flight experience FAR 61.129.
Pilot certification in the US on Wikipedia.
Process for foreign CPL to FAA-PPL conversion (FAR 61.75).
Flight Instructors FAR 62.181

Could you clarify your remark that "A valid residence permit will be necessary to use the FAA-CPL"?  Where is this requirement, and what if the aircraft was being flown outside the US?

I'm not a US citizen. I refer to the section Non-Resident Workers in Can foreign pilots get an FAA ATPL and work for a US-based commercial airline? for the case of a pilot without a Green Card. My understanding is that you cannot be employed by an airline. Am I wrong here? For what it is worth, this discussion on PPRuNe, very confused.


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How useful are simulators in pilot training?
For commercial pilots' training, airlines rely heavily on the training at computer simulators (fixed base simulators), where one can learn the cockpit controls and how to use the cockpit displays to control the airplane. But this does not give them the physical feel of controlling the airplane (which can be felt while using a real physical simulator (Hydraulic Simulators), as used by NASA in training their astronauts). Do airlines use such physical simulators to train pilots or are computer simulators the only ones used? Moreover, what is the usefulness of simple computer simulators as such then?
As a follow-up, do military pilots undergo training in physical real life simulators or they too are trained first in the computer simulators and then directly in the training planes?

Just to verify, you are asking about the usefulness of fixed-base (stationary) simulators vs full-motion (hydraulic) simulators? Or do you have different simulators in mind?

You guessed that right!! Edited the question to make it less ambiguous

For use of software simulators, this question has detailed discussions.

When I went through USAF pilot training...
Useful? Absolutely invaluable. Many of our instructors had experience before "real" simulators were used in training. All of them commented on how obviously better we were on our very first actual flight.
We had "cockpit familiarization" trainers. This looked like a cockpit, sat still on the floor, had all the switches but all they did was switch. They did nothing. We practiced "switchology", checklists, and so forth. Beyond required time and tasks in this thing we could spend free time playing around with these. Not unlike checking out a book from the library.
The above are very useful because it kept the "real" simulators available for actual flight training.  We had quite a few hours in this simulator before we got in a real airplane. And simulator training continued throughout the year in flight school.

But this does not give them the physical feel of controlling the airplane

Yes it does. But as we got more expert in the aircraft, flying every day, sometimes twice a day, we could tell the difference. But the simulator feel was quite good and in no way did it hinder acquiring the touch for precision, when in formation for example.

As someone who works on commercial flight simulators I hope I can help answer your questions.
In a typical training environment you find the following:
Computer Based Training
Custom designed applications are provided by various manufacturers and they are designed to represent/simulator the entire aircraft, or they can focus on a specific system like the Flight Management System.
Examples include
CAE Simfinity
Aerosim
These tools are valuable because they can run on most any computers, and even tablets now, thus allowing the student to learn at their own pace without tying up an actual training device.
Flight Training Devices
These are physical mock ups of the aircraft cockpit in question, there are various levels that these can be certified to that (mostly) relate to the hardware configuration. These are typically used for initial training only. These are fixed based and usually do not include any out the window visuals.
Full Flight Simulators
A full flight simulator provides a complete representation of the simulated aircraft in question. It consists of a fully accurate flight deck, a visual system, a control loading system and a motion system. There are 4 levels of certification a full flight simulator can receive (A, B, C and D) with D being the highest one currently. A level D simulator consists of a 6 degrees of freedom motion system as well as a wrap around collimated visuals. Level D simulators must provide additional special effects and cues to the pilot and there are more quality tests that are required to be run to demonstrate the simulator matches the aircraft.
To answer your question, airlines most definitely do make use of full flight simulators and they are incredibly useful. The average level D simulator might cost $15 million dollars but it is a small fraction of the cost required to train on the real aircraft (factoring in fuel and maintenance etc.), stats I've read show that FFS training can be as much as 1/40th the cost of using the real aircraft. In addition to the cost savings, they allow crews to train for situations that would be too dangerous or impossible to simulate using a real aircraft (for example a sudden engine seizure at V1, among many others).
The advantage of a level D simulator is that it is certified to allow zero flight time training, where the first flight a pilot flies is a revenue flight. Full flight simulators are used in both initial and recurrent pilot training.

Flight training devices (FTD) are the non-moving, no-visuals cockpit replicas you seem to be reference as "computer simulators".  These provide a real cockpit layout (real avionics, switches, buttons, etc) that are used as procedure trainers and to learn cockpit flows.  The main purpose of these is so you are aren't wasting time in the expensive full flight simulator and can get right to work once you get in there.
Once FTD training is finished, you move into the full flight simulator (FFS, typically a level-D sim per FAA certification) which are simulators with exterior visuals and a 6-axis hydraulic motion platform.  These are the devices used for the actual flight training in airline training.  You are expected in your first sim session to already know your way around the cockpit and not be too distracted by where all the buttons you need are so you can focus on the flight training.  Being at that comfort level for the first sim session is the purpose of spending time in the FTD to start.


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What are the pros and cons of having canard control surfaces versus a horizontal tail control surface?
For a normal civil aviation aircraft, what are the pros and cons of having Canard control surfaces or horizontal tail control surface?

You might find enough information to answer your question here and maybe here.

For statically stable aircraft, the canard is a spoiler in disguise. It will create a strong downwash right behind itself, coupled with an upwash outward of $\pi$/4 of its semispan. With changing angle of attack and lift coefficient, the vertical position and the strength of both up- and downwash will change, so the wing incidence variation over wingspan can be made right for just one angle of attack.
Pros

The force to effect flight path changes works the right way, so pitch response times of canards are slightly better than those of a conventional configuration.
The wing can be further aft, so in short business jets the cabin might not interfere with the wing spar.

Cons

The induced drag at off-design points is higher than that of a comparable conventional configuration.
The bigger lifting surface must keep some stall margin, so the total lift coefficient will be smaller than that of a comparable conventional configuration. In the end, a canard will need more wing area.
Control surface deflections will add to the already high lift coefficient of the canard plane, increasing lift demands on the surface with the smallest margins.
The highest lift coefficient is needed at the surface with the smaller Reynolds number. Normally, the reverse would be better.
If the engines are mounted below and ahead of the wing, they will be hit by the wake of the canard, reducing intake efficiency and compressor stall margins.
To make sure that the control surface will be the last thing on the plane to run into compressibility problems, it should have less lift coefficient and more sweep than the wing. In the end, a statically stable canard will have a lower cruise Mach number than a comparable conventional configuration.
The landing gear must be made to retract into the fuselage, because the wing is too far behind the center of gravity to allow the gear to retract into the wing.

I could go on, but I guess you see by now where this is heading …

It should be mentioned that this assumes aircraft designed to be stable in pitch (as most are). For unstable fighter most of the cons go away.

@JanHudec: Yes, right. But try to design an unstable civil aviation aircraft: The opposition to the relaxed stability of the A310 was already substantial - going for an unstable configuration has never been tried.

Why is it that you do not mention (or at least discuss) the reduction in overall trim drag as a result of both wing surfaces generating lift in the same direction instead of opposing one another? I always thought that this was an advantage of the canard in (e.g., Rutan designed canard aircraft)

@CharlesBretana This is superficially true, but only shows how poor conventional designs compare to good canards. What counts is the sum of all parts which can be seen in a Treffz plane behind the airplane. Sometimes a negative load on the tail even reduces induced drag.